1. Field of the Invention
The present invention relates to the reduction of impurities in dialkyl peroxides. More particularly, the present invention relates to a method for reducing the concentration of dialkyl ethers in dialkyl peroxides.
2. Description of Related Art
Methyl t-butyl ether (MTBE) is a by-product formed during the manufacture of di-t-butyl peroxide (DTBP). MTBE is a suspected threat to human health. When DTBP is used to cross-link polyethylene (PE) pipe that may be used to transport potable water, the MTBE becomes an unwanted contaminant in the pipe. The MTBE can be leached out from the pipe and render the water foul-smelling and, possibly, hazardous to human health. See Announcement of the Drinking Water Contaminant List (Mar. 2, 1998, 63 FR 10273–10287).
Two reports in the literature that state that MTBE is formed as one of the decomposition products of DTBP are Batt, L. et al., J. Chemical Physics, 36:895–901 (1962) and Val'kovskii, D. G. et al., Izv. Akad. Nauk SSSR, Ser. Khim. 7:1319–27 (1963), (C. A. 59:68797).
Two patents report general methods for the purification of DTBP:
U.S. Pat. No. 4,900,850 discloses that a tertiary butyl alcohol/ditertertiary butyl peroxide azeotrope may be recovered from a product containing tertiary butyl alcohol and ditertiary butyl peroxide by distilling the tertiary butyl alcohol product to obtain an overhead fraction containing substantially all of the ditertiary butyl peroxide as a ditertiary butyl peroxide/tertiary butyl alcohol azeotrope and other contaminants. It is also disclosed that the ditertiary butyl peroxide can be recovered from the distillate fraction by extraction with water (e.g., in a countercurrent water extraction tower) to provide a ditertiary butyl peroxide product of any desired degree of purity.
U.S. Pat. No. 5,453,548 discloses a process for the separation of ditertiary butyl peroxide from tertiary butanol that includes the step of dehydrating the tertiary butanol to isobutylene and water.
The following three references indicate the treatment of DTBP with concentrated sulfuric acid caused significant degradation of the peroxide:
U.S. Pat. No. 3,917,709 discloses that tertiary aliphatic hydroperoxides and peroxides in the presence of a highly concentrated acid catalyst are converted to a mixture of ketones and alcohols in substantially quantitative yields. The corresponding secondary aliphatic hydroperoxides yield product mixtures of alcohols, ketones and aldehydes in varying proportions, depending upon the acid concentration employed.
Milas, N. et al., J. Am. Chem. Soc. 68:205–208, (1946) reported that when DTBP was dissolved in concentrated sulfuric acid, a polymeric hydrocarbon slowly separated from the solution.
Solyanikov, V. M. et al., Izv. Akad. Nauk SSSR, Ser. Khim. 6:1400–2 (1976) (C. A. 85:123082) reported that DTBP was decomposed by hydrochloric, perchloric, and sulfuric acids. This acid-catalyzed decomposition is said to give Me3C+ and Me3COOH. Deprotonation of the Me3C+ yields isobutene and homolysis of the Me3COOH yields free radicals.